Method of Forming Automobile Sound Absorbing Member through Molding

ABSTRACT

Disclosed is a method for producing an automobile sound absorbing member through molding. In the method, a first fiber and a second fiber are bonded to each other and molded at the same time, so that a working process and a process cycle are simplified, thereby improving production speed and reducing investment for equipment and facility. The method includes (a) preparing a first fiber and a second fiber, (b) providing an adhesive member between the first fiber and the second fiber and placing an aggregate of the first fiber, adhesive member, and the second fiber in a molding machine, and (c) pressing an upper mold and a lower mold of the molding machine so that the first fiber and the second fiber are bonded and molded into a molded body.

TECHNICAL FIELD

The description in the present specification relates to a method ofproducing a sound-absorbing member with improved sound-absorbingperformance for automobiles through molding.

BACKGROUND ART

Unless otherwise stated herein, the statements in this specificationmerely provide background information related to the present disclosureand do not constitute prior art.

The internal/external noise that enters the interior of a vehiclethrough various routes during vehicle driving causes discomfort to thedriver and the occupants. These noises mainly include noise generatedfrom the engine and noise generated from the vehicle exhaust. As amethod of solving the problem of noise entering the interior of avehicle, sound absorbing materials are applied to various vehiclecomponents, such as a headliner, a door trim, a rear shelf, a truck mat,a car mat, and a bonnet.

For a sound absorber for a vehicle, Patent Document 1 discloses a methodincluding the steps of: cutting a back felt containing low-meltingfiber; preheating the back felt; bonding the back felt and a piece ofcarpet fabric to each other by placing the carpet fabric on the surfaceof the back felt and inserting the resulting stack of the carpet fabricand the back felt into a mold for molding so that the melted low-meltingfiber flows into the carpet fabric during the preheating; and cooling amolded body made of the carpet fabric and the back felt.

According to Patent Document 1, the felt is separately preheated andthen molded and cooled in the mold. Therefore, the appearance qualityand sound absorption performance are deteriorated, and the productionspeed is slow because the production method is complicated.

DISCLOSURE Technical Problem

The objective of the present disclosure is to provide a method ofmolding a sound-absorbing material for automobiles, the method beingsimple and being capable of producing a sound absorbing member with goodsurface quality and improved sound-absorbing performance.

Technical problems that can be solved by the present disclosure are notlimited to the above-described objective, and other technical problemsthat are not described herein can also be solved by the presentdisclosure.

Technical Solution

According to one embodiment of the present disclosure, there is provideda method of molding a sound absorbing material for a vehicle, the methodincluding: (a) preparing a first fiber and a second fiber; (b) providingan adhesive member between the first fiber and the second fiber andplacing an aggregate of the first fiber, adhesive member, and the secondfiber in a molding machine; and (c) pressing an upper mold and a lowermold of the molding machine so that the first fiber and the second fiberare bonded and molded into a molded body.

In addition, in step (a), each of the first fiber and the second fiberincludes 50% to 95% by weight of at least one base fiber selected frompolyethylene terephthalate, polypropylene, polyacrylate, nylon, andcotton and 5% to 50% by weight of a binder fiber having a melting pointof 200° C. or below, the first fiber has an areal density of 600 to 1400g/m², and the second fiber has an areal density of 600 to 2000 g/m².

In addition, in step (b), the adhesive member is composed of at leastone layer, is made of at least one selected from polyethylene,polypropylene, ethylene vinyl acetate copolymer, polyamide, andlow-melting-point polyethylene terephthalate, and has a thickness of 30to 200 μm.

In addition, in step (c), the upper mold may perform a vacuuming processfor 40 to 50 seconds under a temperature condition of 10° C. to 100° C.

In addition, in step (c), the lower mold may perform a steaming processand a vacuuming process at least twice.

In addition, in the steam process, steam or hot air of 100° C. to 200°C. may be supplied for 5 to 15 seconds at a pressure of 1 to 5 bar.

In addition, in step (c), the vacuum process may be performed for 1 to15 seconds under a temperature condition of 100° C. to 200° C.

In addition, after step (c), (d) trimming may be performed afterremoving moisture remaining on the surface of the molded body dischargedthe molding machine.

Advantageous Effects

In the automobile sound absorber molding method according to oneembodiment disclosed in the present specification, the bonding of thefirst fiber and the second fiber and the molding are performed at thesame time. This simplifies the working process and process cycle,thereby improving the production speed and reducing the cost ofinvestment for equipment.

In addition, by processing the first and second fibers at differenttemperatures with different processes, instead of using a conventionalmethod performing cold pressing after preheating the first and secondfibers, the method has the effect of improving the appearance qualityand sound absorbing performance while minimizing damage to the surfaceof the first fiber.

In addition, since vertical fiber is used as the second fiber, thethickness of the second fiber can be reduced, resulting in reduction inweight of a final product (i.e., a sound absorber).

DESCRIPTION OF DRAWINGS

FIG. 1 is a process flowchart illustrating a method of molding a soundabsorbing material for a vehicle according to an embodiment in thepresent disclosure;

FIG. 2 is a schematic view illustrating a method of molding a soundabsorbing material for a vehicle according to an embodiment in thepresent disclosure;

FIG. 3 is a photograph illustrating a sound absorber according toExample 1;

FIG. 4 is a schematic view illustrating a method of molding a soundabsorbing material according to Comparative Example 1;

FIG. 5 is a photograph illustrating a sound absorber of ComparativeExample 1; and

FIG. 6 is a graph showing a result of evaluation of sound absorbingperformance according to Experimental Example 1.

BEST MODE

The advantages and features of the present disclosure and the manner ofachieving them will become apparent with reference to embodimentsdescribed in detail below and the accompanying drawings. The inventionmay, however, be embodied in many different forms and should not beconstrued as being limited to the embodiments set forth herein. Rather,these embodiments are provided so that the invention will be thoroughand complete and will fully convey the concept of the invention to thoseskilled in the art. Thus, the invention will be defined only by thescope of the appended claims. Like reference numbers refer to likeelements throughout the description herein and the drawings.

Further, in describing embodiments of the present disclosure, well-knownfunctions or constructions will not be described in detail since theymay unnecessarily obscure the gist of the present disclosure. Thefollowing terms are defined in consideration of the functions in theembodiments of the present disclosure and thus may vary according to theintentions of users, operators, or the like. Therefore, the definitionof each term should be interpreted based on the contents throughout thisspecification.

Hereinafter, a method of molding a sound absorbing material for avehicle according to the present disclosure will be described in detailwith reference to the accompanying drawings.

FIG. 1 is a process flowchart illustrating a method of molding a soundabsorbing material for a vehicle according to an embodiment of thepresent disclosure, and FIG. 2 is a schematic view illustrating a methodof molding a sound absorbing material for a vehicle according to anembodiment of the present disclosure.

Referring to FIGS. 1 and 2 , first, a first fiber 110 and a second fiber120 are prepared (S10).

Each of the first fiber 110 and the second fiber 120 may contain 50% to95% by weight of at least one base fiber selected from polyethyleneterephthalate (PET), polypropylene (PP), polyacrylate (PA), nylon(nylon), and cotton and 5% to 50% by weight of a binder fiber having amelting point of 200° C. or below. Here, as the binder fibers,polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer(EVA), polyamide (PA), and low melting point polyethylene terephthalate(LM PET) may be used.

In the present disclosure, the term “nylon” refers to synthetic polymerbased on aliphatic or semi-aromatic polyamide, and the term “cotton”refers to raw cotton, cotton cloth, and cotton fibers obtained byprocessing cotton as a raw material.

Specifically, in this embodiment, the first fiber 110 is composed of 50%to 95% by weight of the base fiber and 5% to 50% by weight of the binderfiber. Preferably, the first fiber 110 includes 55% to 65% by weight ofthe base fiber and 33% to 45% by weight of the binder fiber. The firstfiber may be manufactured by any one method selected from a needlepunching method, an air-laid method, a fiber blow injection molding(FBIM) method, and a vertical method. The areal density of the firstfiber 110 may be in the range of 600 to 1400 g/m², and preferably in therange of 800 to 1200 g/m².

On the other hand, on one surface of the first fiber 110, any oneselected from elastic rubber such as latex, a polyethylene coatinglayer, compressed fiber, breathable film, non-woven fabric, and adhesivepowder may be provided according to the desired function such asshaping, sound absorbing, insulating, or adhesion.

The second fiber 120 is composed of 50% to 95% by weight of the basefiber and 5% to 50% by weight of the binder fiber. The Second fiber maybe manufactured by any one method selected from a needle punchingmethod, an air-laid method, a fiber blow injection molding (FBIM)method, and a vertical method. The second fiber 120 is a vertical fiberhaving a verticality of about 40° to 90° which has excellent elasticityand breathability, thereby facilitating a molding process to bedescribed later. The second fiber 120 has an areal density in the rangeof 600 to 2000 g/m² and preferable in the range of 800 to 1400 g/m². Inaddition, unlike a conventional method in which the second fiber has tohave a thickness larger than or equal to the maximum thickness of anapplication component for good adhesion with the first fiber 110,according to the present disclosure, sufficient adhesive strengthbetween the second fiber and the first fiber 110 can be obtained evenwhen the second fiber is thin. Since the thickness of the second fiberis reduced, the weight of the sound absorbing member, which is the finalproduct, can be reduced.

Next, the adhesive member 130 is provided between the first fiber 110and the second fiber 120 and then an aggregate of the first fiber 110,the adhesive member, and the second fiber 120 is placed in a moldingmachine 1000 (S20).

That is, an object in which the adhesive member 130 is provided betweenthe first fiber 110 and the second fiber 120 is placed in the moldingmachine 1000. In this case, the aggregate may be a stacked structure inwhich the second fiber 120, the adhesive member 130, and the first fiber110 are stacked in this order from the bottom.

The adhesive member 130 is not significantly limited in specificmaterial as long as the material has a melting point of 200° C. orbelow, but any at least one material selected from polyethylene (PE),polypropylene (PP), ethylene vinyl acetate copolymer (EVA), polyamide(PA), and low-melting polyethylene terephthalate (LM PET) may be used.Preferably, either polyethylene (PE) or polyamide (PA) is used. Theadhesive member 30 may be applied in various forms such as a film, aliquid adhesive, a fiber, a hot melt, an adhesive fiber, a powder, acoating layer, etc. to facilitate adhesion of the first fiber 110 andthe second fiber 120. As the film, a breathable film may be used.

In this embodiment, the adhesive member 130 may be formed as at leastone layer. Preferably polyamide, the adhesive member 130 may be athree-layer film in which polyethylene is provided as an intermediatelayer and polyamide is provided on and under the polyethylene. In thiscase, the thickness of the adhesive member 130 may be in the range of 30to 200 μm. Preferably, the thickness is 50 μm. When the thickness of theadhesive member 130 is smaller than 30 μm, the adhesive strength can beeasily lost. On the other hand, when the thickness exceeds 200 μm, thethickness of the final molded body 100 becomes excessively thick, whichis not preferable in terms of its use.

Next, an upper mold 1100 and a lower mold 1200 of the molding machine1000 are pressed against each other to bond and mold the first fiber 110and the second fiber 120 to each other (S30).

The molding machine 1000 is composed of the upper mold 1100 for moldingthe first fiber 110 and the lower mold 1200 for molding the second fiber120, and the upper mold 1100 and the lower mold 1200 has at least onehole serving as an air intake passage on the surface thereof. The uppermold 1100 and the lower mold 1200 of the molding machine 1000 hotpresses the first fiber 110 and the second fiber 120 in a directionperpendicular to the ground surface for 40 to 50 seconds, and morepreferably for 45 seconds to perform bonding and molding simultaneously.

On the other hand, the upper mold 1100 and the lower mold 1200 eachperform different processes, but the upper mold 1100 performs avacuuming process, and the lower mold 1200 performs a steaming processand a vacuuming process at least two times.

The vacuuming process performed by the upper mold 1100 is a process ofcontinuously suctioning air for 40 to 50 seconds and preferably for 43to 47 seconds through the hole(s) formed on the surface of the uppermold 1100. This vacuuming process may be carried out at a temperature inthe range of 10 to 100° C., preferably in the range of 30° C. to 70° C.,and most preferably in the range of 40° C. to 60° C., so that thetemperature of the upper mold 1100 is not excessively high because theexcessively high temperature may cause damage to the surface of thefirst fiber 110. As described above, since the first fiber 110 is moldedin the vacuuming process under a low temperature condition, damage tothe surface of the first fiber 110 is minimized. Therefore, theappearance quality and the sound absorption performance of the productare improved.

The vacuuming process performed by the lower mold 1100 is a process ofcontinuously suctioning air for 1 to 15 seconds and preferably for 5 to10 seconds through the hole(s) formed on the surface of the lower mold1200. This vacuuming process may be carried out at a temperature in therange of 100 to 200° C. and preferably in the range of 130° C. to 170°C. so that damage to the surface of the second fiber 1200 can beprevented and the adhesive member 130 can be melted.

The steaming process performed by the lower mold 1200 is performed bysupplying steam or hot air of 100° C. to 200° C., preferably 130° C. to170° C., and most preferably 140° C. to 160° C. at a pressure of 1 to 5bar and preferably 2 to 4 bar for a period of 5 to 15 seconds.

In the present embodiment, the lower mold 1200 may sequentially performa first steaming process, a first vacuuming process, a second steamingprocess, and a second vacuuming process.

For example, the first steaming process may be carried out by ejectingsteam or hot air of 140° C. to 160° C. at a pressure of 2 to 4 bar for 8to 12 seconds, and the first vacuuming process may be performed for 8 to12 seconds. The second steaming process may be performed by ejectingsteam or hot air of 140° C. to 160° C. at a pressure of 2 to 4 bar for 3to 7 seconds, and the second vacuuming process may be performed for 3 to7 seconds. The first vacuuming process and the second vacuuming processmay be performed in a temperature range of 140° C. to 160° C., andspecifically, the temperature of the lower mold 1200 may be in the rangeof 140° C. to 160° C.

In the process of bonding and molding the fiber with the above-describedmolding machine 1000, the first fiber 110 placed in the molding machine1000 is seated and molded by the vacuuming process performed by theupper mold 1100, and the second fiber 120 is bonded to the first fiberand molded by the lower mold 1200 in a manner that the adhesive material130 is melted by the steaming process of the lower mold 1200 to bebonded the first fiber 110 and the second fiber 120 is molded by thevacuuming process. In addition, during the vacuuming process, the secondfiber 120 heated by the steaming process may be cooled.

Finally, after removing moisture remaining on the surface of the moldedbody 100 in the molding machine 1000, the surface of the molded body 100is trimmed (S40).

In step S30, a hot air blower 2000 may blow room temperature air ormildly heated air to remove the moisture remaining on the surface of themolded body 100 obtained in step S30, and then the molded body 100 istrimmed into a desired shape. The molded body 100 may be asound-absorbing member for use in the interior of a vehicle.

Preparation Example 1. Preparation of First Fiber

After mixing 60% by weight of polyethylene terephthalate (PET) and 40%by weight of a binder fiber, a needle punching process was performed onthe mixture to produce a first fiber having an areal density of 800g/m².

Preparation Example 2. Preparation of Second Fiber

After mixing 70% by weight of polyethylene terephthalate (PET) and 30%by weight of a binder fiber, an air laid process was performed on themixture to produce a second fiber having an areal density of 1200 g/m².

Preparation Example 3. Preparation of Adhesive Member

Polyethylene (PE), polyamide (PI), and polyethylene (PE) were laminatedand pressed to prepare an adhesive member in the form of a three-layerfilm having a thickness of 50 μm.

Example 1. Preparation of Sound Absorbing Member

The first fiber, the second fiber, and the adhesive member prepared inPreparation Examples 1 to 3 were mounted in a hot forming mold withoutbeing preheated. Then, the upper mold was heated to 50° C. and avacuuming process was performed for 45 seconds. At the same time, asteaming process was performed such that the lower mold was heated to180° C., and then steam of 150° C. was applied at a pressure of 3 barfor 10 seconds, and then a vacuuming process was performed for 10seconds. Next, another steaming process was performed such that steam of150° C. was applied at a pressure of 3 bar for 5 seconds, and thenanother vacuuming process was performed. Thus, a sound absorbing memberwith a double layer structure shown in FIG. 3 was obtained.

Comparative Example 1. Preparation of Sound Absorbing Member

As shown in FIG. 4 , first, a second fiber was preheated in a hot airoven at 180° C. for about 80 seconds and then pressed and molded in acold forming machine at 25° C. for 50 seconds. The molded second fiberwas placed in a cold forming mold having a temperature of 25° C. Thefirst fiber and the adhesive member were preheated for about 80 secondsin a hot air oven at 180° C., and then laminated on the second fiber andpressed for 60 seconds to prepare a sound absorbing member having adouble layer structure shown in FIG. 5 .

Experimental Example 1. Sound Absorption Performance Evaluation

An experiment was conducted according to ISO 10354-2 using a verticalincident sound absorption coefficient tester (Two-microphone ImpedanceMeasurement Tube) to evaluate the sound absorption performance of thesound absorption member of Example 1.

The sound absorption performance was measured from the side of the firstfiber of the sound absorption member, and the results are shown in Table1 and FIG. 6 .

TABLE 1 Frequency Comparative (Hz) Example 1 Example 1 400 0.19 0.35 5000.19 0.39 630 0.20 0.43 800 0.21 0.44 1,000 0.22 0.44 1,250 0.23 0.441,600 0.31 0.48 2,000 0.33 0.51 2,500 0.29 0.41 3,150 0.30 0.37 4,0000.38 0.40 5,000 0.51 0.52

Referring to Table 1 and FIG. 6 , it was confirmed that the soundabsorbing member of Example 1 was significantly superior to the soundabsorbing member of Comparative Example 1 at all frequencies. Therefore,it was found that the surface damage of the first fiber attributable toheating affects the sound absorption performance.

Although the exemplary embodiments described herein and theconfigurations illustrated in the drawings are presented forillustrative purposes and do not exhaustively present the technicalspirit of the present disclosure. Accordingly, it should be appreciatedthat there will be various equivalents and modifications that canreplace the exemplary embodiments and the configurations at the time atwhich the present application is filed. Therefore, it should beunderstood that the above-described embodiments are considered to beillustrative in all respects but are not considered as to berestrictive. The scope of the present disclosure should be defined bythe appended claims rather than the foregoing description, and allchanges or modifications that can be derived from the meaning, scope,and equivalent concept of the claims should be construed as fallingwithin the scope of the present disclosure.

1. A method of producing an automobile sound absorbing member throughmolding, the method comprising: (a) preparing a first fiber and a secondfiber; (b) providing an adhesive member between the first fiber and thesecond fiber and placing an aggregate of the first fiber, the adhesivemember, and the second fiber in a molding machine; and (c) pressing theaggregate with an upper mold and a lower mold of the molding machine sothat the first fiber and the second fiber are bonded and molded at thesame time, wherein the upper mold and the lower mold perform differentprocesses, respectively.
 2. The method of claim 1, wherein in step (a),each of the first fiber and the second fiber comprises 50% to 95% byweight of at least one base fiber selected from polyethyleneterephthalate, polypropylene, polyacrylate, nylon and cotton and 5% to50% by weight of a binder fiber having a melting point of 200° C. orbelow, and the first fiber has an areal density in a range of 600 to1400 g/m², and the second fiber has an areal density in a range of 600to 2000 g/m².
 3. The method of claim 1, wherein in step (b), theadhesive member is composed of at least one layer, comprises at leastone material selected from polyethylene, polypropylene, ethylene vinylacetate copolymer, polyamide, and low-melting-point polyethyleneterephthalate, and has a thickness in a range of 30 to 200 μm.
 4. Themethod of claim 1, wherein in step (c), the upper mold performs avacuuming process for 40 to 50 seconds under a temperature condition of10° C. to 100° C.
 5. The method of claim 1, wherein in step (c), thelower mold performs a steaming process and a vacuuming process at leasttwo times.
 6. The method of claim 5, wherein in the steaming process,steam or hot air of 100° C. to 200° C. is supplied for 5 to 15 secondsat a pressure of 1 to 5 bar.
 7. The method of claim 5, wherein thevacuuming process is performed for 1 to 15 seconds under a temperaturecondition of 100° C. to 200° C.
 8. The method of claim 1, wherein afterstep (c), (d) trimming is performed after removing moisture remaining onthe surface of a molded body manufactured by the molding machine.